The invention pertains to cooling beds for heated cast metal bars whereby the rate of cooling may be closely regulated.
In the casting of metal bars, such as of steel, the steps basically include melting, casting, reheating, descaling, rolling, sawing to length, and cooling. These steps can be sequentially continuously performed with known apparatus, for instance, such as with rotational casters, and high production can be achieved with a minimum of equipment and investment.
However, one of the serious problems that has existed with known apparatus of this type lies in the inability in such a continuous processing system to accurately control the rate of heat transfer at the last metal cooling step so as to selectively produce a "soft" bar substantially free of internal stress and which has superior shearing and mechanical characteristics or a "hard" bar which has high wear resistance. Conventional cooling beds receiving the hot metal bars from the saw retain the bar upon conveyors open to the air, and by conduction, radiation and convection the bars will relatively rapidly cool at an uncontrolled rate, often resulting in a "hard" bar which cannot be readily sheared, when a "soft" bar is desired, and which is internally stressed because of the relatively rapid cooling.
In the conventional processing of ingots and bars internal stresses are relieved by normalizing the metal after leaving a cooling bed, and after the metal has substantially cooled. Such normalizing requires that the bars be reheated, and "soaked" in a soaking pit or other apparatus which permits the bars to slowly cool. Such reheating of the metal requires additional handling, extensive additional energy consumption and time, and a very expensive.